_RL k12p
k12p = k1plocal*k2plocal
k123p = k12p*k3plocal
a = x3 + k1plocal*x2 + k12p*x + k123p
da = 3.0*x2 + 2.0*k1plocal*x + k12p
& pt*k12p*x/a +
& (pt*k12p*(a - x*da))/a2 -